Process of treating crude sulfate soap skimmings



surface of the black liquor.

Patented May 9, 1950 UNITED STATES PATENT OFFICE PROCESS OF TREATINGCRUDE SULFATE SOAP SKIIVIMINGS No Drawing. Application January 9, 1947,Serial No. 721,144

Claims. 1

The present invention relates to the art of treating crude sulphate soapskimmin'gs to refine them, and more particularly, to a process ofconverting crude sulphate soap skimmings into a dried soap powder whichdoes not have any of the bad characteristic odors of the material.

It is well known in the paper and pulp industry that when black liquorfrom the sulphate process is evaporated, a scum, known as black sulphatesoap skimmings, separates and floats upon the Generally speaking, suchskimmings contain black liquor with sodium sulphide, sodium sulphate,mercaptans, sodium lignate, and many other sulphate paper-mill Yproducts.

A typical analysis of the soap skimmings is as follows:

Per cent Sodium salts of fatt acids 30 Sodium salts of rosin acids 30Unsaponifiables 4 Sodium lignate 3 Black liquor solution solids) 33 Asthe art knows, the black sulphate soap skimcan then be used industriallyfor many operations. Thus, for example, it can be saponified for varioususes, or the crude tall oil can be refined by distillation and solventtreatment to get rid of th obnoxious odors and to improve color, etc.,after which it can be saponified and used for various soaps, lubricants,etc.

It has been found that when crude sulphate soap skimmings are taken anddried, as in a spray drier, nearly all of the bad properties areeliminated. When crude sulphate soap skim- -mings are first washed with,for instance, a five per cent sodium chloride solution, or other alkaliwhich will have a tendency to salt out or prevent the soap from goinginto solution, the soluble products, such as the sodium sulphate andsodium sulphide, will dissolve from the crude sodium sulphate soapskimmings and the resulting mate- :rial (that is, the washed blacksulphate soap iskimmings) can be dried in any usual manner. --A productis obtained that is superior to black :sul'phate soap skimmings in thatonly traces of sodium sulphate, sodium sulphide, and black liquor arepresent. The odor is good and the resulting material can be used for avariety of things. We prefer to use the skimmings without washing butthey may be washed with a salt solution if desired.

In drying it has been foundv that spray drying is the method bestadapted to this type of material because a product can be obtained whichis low in moisture and any mercaptans or ill-smelling gases are releasedfrom the soap as it dries in small particles in an atmosphere of hotair.

The soap skimmings are atomized and mixed intermittently with largevolumes of hot air at a high temperature which removes all but traces ofthe ill-smelling components of the soap. It is also believed that whenwater is removed from skimmings down to zero up to about ten per centthe ill-smelling compounds are decomposed and released as gases. Thus,the odor is improved by washing with large volumes of air and bychemical decomposition with heat in the absence of water, the air beingheated to a temperature between substantially 400 F. and 700 F. torapidly vaporize the major portion of the water associated with the soapskimmings and to produce a soap powder having less than 10% of moistureand serving to oxidize ill-smelling sulphur compounds to be taken up bysaid air and permitting the resultin purified soap powder to beseparated from the heated atmosphere of air.

We prefer to first atomize or spray the soap and dry by the methodcommonly known as spray drying because of the large volumes of hot airused. This removes the moisture, decomposes the ill-smelling compoundsand then washes them out. This is accomplished in one operation. Anillustrative example is given as follows:

A spray tower about 18 feet in diameter and about 18 feet high, equippedwith gas air heater, and capable of producing heated air up to 700 F.,was used. The suction fan bottom of the tower was approximately fourfeet in diameter and had six blades. The bottom of the spray tower wasequipped with air-propelled sweeper slotted to receive dry material bysuction. From the bottom, the material passed to a conical dustcollector. The top of the tower was equipped with a high-speed atomizeror sprayer. The material was added to an atomizer or sprayer equipmentby gravity feed or by a pump equipped preferably with a Reeves drive.

Approximately 200- pounds of sulphate soap skimmings were dumped into acopper jacketed kettle with a lightning mixer. To the skimmings wasadded about 50 pounds of water. This gave a mixture of approximately 50per cent solids. While the mass was mixing, steam was applied to thejacket and the material was heated to about 160 F. This produced amaterial which would flow and which was easily pumped to the atomizer orsprayer.

The temperature of the air in the chamber was about 410 F. and the speedof the atomizer or sprayer was about 6200 R. P. M. The rate of flow wasabout ten pounds of liquid per minute or about five pounds per minute ofsolid material. A sample was taken off the floor of the spray toweritself. This material had a bead-like form and was very light in weight.The material had good color and excellent odor. Samples were taken fromthe bottom of the tower itself and also from the conical dust collector.The material passing through the conical dust collector was changed to apowder.

A vacuum drier can be used, if desired, but is not as eilicient as aspray drier. In a test run with a four tray vacuum drier, approximatelyfour feet by four feet, using about to of vacuum, the soap was dried inapproximately from four to six hours. When originally poured into thepans the material represented approximately 50 per cent solids andcovered the bottom of the pan to approximately one-half inch. Afterbeing dried, the material was reduced to approximately one-quarter inchand was in a sheet form which broke up very readily into large flakes.

The material had good odor, but it was not quite as good as the spraydried material. In the vacuum drying operation, the vacuum pulled mostof the obnoxious odors from the soap skimmings along with the moisture.

A drum drier may be used, but it is the least eflicient of the three.This method does not wash the product with gases as in the foregoingoperations. It only accomplishes the desired results by heat and byremoving water. Thi type may be used with about 0 per cent solids andabout 60 per cent water and introduced on a drum three feet by fivefeet, equipped with doctor blade. Steam at 100 pounds pressure is usedin the drum to dry the material poured on the face of the drum. Thesolution is introducedor fed onto the drum so that the production rateis approximately 300 pounds per hour.

The resulting which can be called tallate" or sodium talllte, can beused industrially in a number of ways, due to the fact that it does nothave a bad characteristic odor. For

instance, the material can be used as common Various treatments havebeen proposed to eliminate the objectionable features of black liquorsulphate soap skimmings, but as far'as is known) none has been whollysatisfactory and successful, especially when carried into'practice on anindustrial scale for the production or commercial products.

From the foregoing, it can be seen that great savings can be effectedtreating the sulphate soap skimmings directly by the present invention.

The practice in the trade at the present time is to take the crudesulphate soap skimmings, split them with sulphuric acid, produce talloil and throw away the lignin and the sodium content as sodium sulphate.Ordinary sulphur compounds are liberated as hydrogen sulphide, althougha small percentage of these remain dissolved in the crude tall oil Whichstill gives it an objectionable odor. In order to get rid of this odor,the crude tall oil is refined by distillation, solvent process, etc. Therefined product is then re-saponified with caustic soda to producesodium tallate, or the sodium salt of tall oil. It is to be noted thatthis is the same material that came from the paper mills, but, ofcourse, minus the impurities from sulphate paper manufacture.

In our process the crude sulphate soap skimmings are taken as is, orwashed, if necessary, and then are directly heated and dried to producedry sodium tallate. The sulphur compounds are decomposed and liberatedand washed by the large volume of gases so that the resulting materialcan be used in industry as is. Thus, in one step a product is producedby the present invention which ordinarily requires three steps in priorprocesses.

It will be understood that the method of the present invention has beendescribed in its preferred form and that various changes or modifications may be made therein without departing from the spirit or scopeof the invention as defined in the claims annexed hereto.

Having thus described the invention, what is claimed as new is: I

A method for the direct production of a purified soap powder from liquidcrude sulphate soap skimmings obtained from black liquor which comprisesspray-drying said liquid soap'skimmings by atomizing the same into anatmosphere of air heated to a temperature from about 400 F. to about 700F. to form a soap powder having not more than about 10% of moisture andto transform ill-smell'ng ingredients in said soap skimmings to volatilecompounds of relatively inoffensive odor taken up by the said atmosphereand separating the resulting soap powder from the said atmosphere whilein a heated condition to retain the moisture therein.

2. A method for the direct production of purified soap powder fromliquid crude sulphate soap skimmings obtained from black liquor whichcomprises heating said liquid soap skimmings to a readily-lowingconsistency, feeding the heated soap slzimmings by gravit feed to a highspeed atomizer, washing the atomized soap skimmings with a large volumeof air without the addition of water, said being heated to a temperaturebetween substantially 400 F. and 7&0" F. to rapidly vaporize the majorportion of the water associated with the soap skimmings to produce asoap powder having less than 10% of moisture and serving to oxidizeill-smelling sulphur compounds to be taken up by said air and separatingthe resulting soap powder from the heated atmosphere of air.

3. A method for the direct production of minifled soap powder fromliquid crude sulphate soap skimmings obtained from black liquor whichc'omprises heating said liquid soap skimmings tola temperature of about156 F. to produce a readilyfiowing consistency, feeding the heated soapskimmings to an atomizer in a spray drying apparatus containing airheated to a teui perature between about 400 F. and 700 F. to vaporizewater from the soap skimmings-so as to produce a soap powder therefromhaving not more than 5 10% of moisture and from which ill-smellingingredients have been removed by transformation into volatile relativelyinoffensive compounds taken up by the heated atmosphere, collecting thesoap powder and separating the soap powder from the heated atmosphere ofair.

4. A method for the direct production of purified soap powder fromliquid crude sulphate soap skimmings obtained from black liquor whichcomprises washing the crude sulphate soap skimmings with a salt solutionto prevent the soap therein from going into solution yet dissolvingsoluble salts therefrom, spraying the thus partially purifled liquidsoap skimmings into an atmosphere of air at a temperature of about 410F. to remove moisture from the soap ;material and to oxidizeillsmelling'ingredients originallycontained in the liquid soapskimmings, said oxidized ingredients being taken up by the atmosphere ofair while soap powder having not more than 10% of moisture content isprecipitated in the said atmosphere and removing the said precipitatedsoap powder from the heated air while at a temperature to retain themoisture below the figure given above.

5. A method for the direct production of purifled soap powder fromliquid crude sulphate soap skimmings obtained from black liquor whichcomprises washing the crude sulphate soap skimmings with a solution ofsodium chloride to dissolve sodium sulphide and other soluble saltstherefrom without dissolving any substantial amount of soap therein,heating the partially purified liquid soap skimmings to a readilyflowing consistency, feeding the heated liquid soap skimmings to anatomizer in a chamber containing a relatively large volume of air heatedto a temperature between about 400" F. and 700 F., to absorb themoisture from the liquid soap skimmings and to decompose theill-smelling constituents from the said liquid soap skimrnings to bereleased as gases into the said air, and collecting the purified soappowder.

CLARENCE B. F. YOUNG.

EDWARD J. CALLETON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 19,240 Goodell July 17, 19342,200,468 Cirves May 14, 1940 2,249,365 Dreger Apr, 29, 1941 2,328,892Colgate et a1 Sept. 7, 1943 2,395,282 Lovas et a1. Feb. 16, 19462,399,588 Weston Apr. 30, 1946

1. A METHOD FOR THE DIRECT PRODUCTION OF A PURIFIED SOAP POWDER FROMLIQUID CRUDE SULPHATE SOAP SKIMMINGS OBTAINED FROM BLACK LIQUOR WHICHCOMPRISES SPRAY-DRYING SAID LIQUID SOAP SKIMMINGS BY ATOMIZING THE SAMEINTO AN ATMOSPHERE OF AIR HEATED TO A TEMPERATURE FROM ABOUT 400*F. TOMORE THAN ABOUT 10% OF MOISTURE AND TO TRANSFORM ILL-SMELLINGINGREDIENTS IN SAID SOAP SKIMMINGS TO VOLATILE COMPOUNDS OF RELATIVELYINOFFENSIVE ODOR TAKEN UP BY THE SAID ATMOSPHERE AND SEPARATING THERESULTING SOAP POWDER FROM THE SAID ATMOSPHERE WHILE IN A HEATEDCONDITION TO RETAIN THE MOISTURE THEREIN.